The invention relates, generally, to telemetry systems and, more particularly, to a system for silently alerting inbound-only intelligent communication devices (ICDs) such as telemetry interface units (TIUs), meters, diagnostic processors or the like to facilitate diagnostic, control and data exchange functionality.
It will be appreciated that telemetry systems typically consist of TIUs or other ICDs located on the customer premises where each TIU or ICD is connected to a switching system in the telecommunications network over a customer line such that the TIUs or ICDs can be accessed via the telephone network. One common telemetry system is used to remotely monitor utility usage. The system consists of an "intelligent" utility meter located at the customer premise that records utility usage and communicates with a TIU. The controlling utility establishes a connection with the TIU and the TIU gathers usage data from the utility meter and transmits this information to the utility for billing purposes, usage monitoring or the like. While utility meter reading is a common telemetry application, it will be appreciated that telemetry systems can be used to perform any remote monitoring, measuring, control or diagnostic function.
Different types of TIUs, and associated telemetry systems, have been developed. One known type of TIU is known as an inbound-only TIU. An inbound-only TIU is typically programmed, based upon a stored instruction set, to collect data from a customer device (or to perform a monitoring, diagnostic or control function) and to periodically initiate a call to the entity responsible for controlling the TIU and/or customer device to transfer data or otherwise communicate with the controlling entity. These types of inbound-only TIUs are capable of initiating a call to the controlling entity (inbound communications) but cannot go off-hook to "answer" or complete a connection initiated by the controlling entity. As a result, these inbound-only TIUs cannot be accessed by the controlling entity unless and until the TIU initiates the call.
Some inbound-only TIUs can be alerted by a power ringing alert from the controlling entity. In response to the power ringing alert, the TIU initiates a call to the controlling entity. Typically, the controlling entity makes a standard voice call to the customer premise where the TIU is located and verbally informs the customer that a telemetry "alert" is about to be made to that customer's TIU. The controlling entity then makes a power ringing alert to the customer premise where the TIU is alerted by a power ringing alert that is audible to the customer. Typically, the TIU is alerted after receiving a fixed number of power ringing cycles. As will be appreciated, the audible power ringing alert is extremely disruptive to the customer. As a result, such systems are typically not used at night, when the audible power ringing alert would most disturb the customer even though this is typically the time of day that the telemetry call is least likely to interfere with the customer's regular voice calls. Moreover, it is possible that the TIU will be alerted inadvertently should someone other than the controlling entity call the customer line and inadvertently deliver the power ringing alert signal with the correct fixed number of power ringing cycles. It is also possible that after a number of ringing cycles, but before the fixed number of ringing cycles alerts the TIU, the customer's line may be forwarded to a voice mail system thereby terminating the power ringing before the TIU is alerted.
In addition to the above-discussed inbound-only TIUs, outbound TIUs also exist. Outbound TIUs are capable of answering calls initiated by the controlling entity such that a connection between the controlling entity and the TIU is created at the initiation of the controlling entity. These TIUs provide the advantage that the controlling entity can establish a connection at its initiation at any time. One such outbound system is disclosed in U.S. Pat. No. 5,189,694 issued to Garland on Feb. 23, 1993. This system discloses the use of a suppressed ringing connection where no audible ringing signal is delivered to the customer premise when the alert tone is transmitted to the TIU. Because the TIU answers the tone from the controlling entity and a connection is established between the TIU and the controlling entity, a connection is made every time the controlling entity contacts the TIU. In some circumstances, in response to the initial alert by the controlling entity, the TIU must perform a function such as data retrieval, diagnostics or the like. In such a situation, the connection between the controlling entity and the TIU must either be maintained while the TIU and other related components perform the function or the connection must be terminated while the TIU and other related components perform the function and a second connection must be established later to transmit the data. In either event, network resources are used inefficiently and additional billing charges for the connection time may be incurred by the controlling party.
Thus, a more efficient telemetry system is desired.